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Integration of time series data

Posted on 2009-07-16
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Helo- I have columns of time history data as shown below. How do I do integration of these data and write in a separate column, i. e., in"Integrated values" column? Do I have to use trapizoidal rule, or simpson rule? Any example of MATLAB command or code will help. Thanks.

time Value   Integrated values
0        0.1
0.1     2
0.2     3
0.4     1
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Question by:okd
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by:yuk99
ID: 24873434
What method to use for integration is up to you. Trapezoidal integration is build into Matlab. If you imported time as x and Value as y, you can do integration as z=trapz(x,y);
If you also need help to import/output data, please tell more details on your original data format and what you want as output. How large is the dataset? You can also attach an example here.
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Author Comment

by:okd
ID: 24896016
Thank you. Could you also send me how to import and output data in MATLAB. The database is like I have sent you, but it has 500 rows. I want to plot the time vs. z=trapz(x,y) values. Matlab commands for plotting and import/output data will help the most. Thanks again, - okd
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yuk99 earned 500 total points
ID: 24897374
Here is the code. It read the data from tab-delimited file tsdata.txt and returns 2-column matrix data. To make it clear I put time into time vector and value into value vector (rows 2 and 3). TRAPZ function will return only one value - the total area under the curve for the whole vector. To get integrated value for every time point you can use CUMTRAPZ.
% data import
data=dlmread('tsdata.txt','\t',1,0);
% let's split variables for clarity
time=data(:,1);
value=data(:,2);
% calculating integrated values
intvalue=cumtrapz(time,value);
% plotting
plot(time,intvalue)

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